FIG. 1 illustrates a prior art test system 100 for testing electronic devices. A test controller 102 can provide input signals to the DUTs 118 and can receive response signals generated by the DUTs 118 in response to the input signals. The term “test signals” can refer generically to either or both the input signals generated by the test controller 102 and the response signals generated by the DUTs 118. The test system 100 can include a probe card assembly 112. Electrically conductive probes 114 of the probe card assembly 112 can make pressure-based electrical connections with terminals 116 of the DUTs 118, and the test signals can be passed between the test controller 102 and the DUTs 118 through a connection 104 (e.g., a coaxial cable, a wireless link, a fiber optic link, etc.), electronics (not shown) in a test head 106, connectors 108 between the test head 106 the probe card assembly 112, and the probe card assembly 112. The probe card assembly 112 can be coupled to a mounting surface 110 of a housing 120 (e.g., a prober) that includes a moveable chuck 122 on which the DUTs 118 are disposed. The chuck 122 can move the DUTs 118 such that terminals 116 of the DUTs 118 are pressed against probes 114 of the probe card assembly 112. Alternatively or in addition, the probe card assembly 112 can be moved.
As shown in FIG. 2, the probe card assembly 112 can include multiple substrates. For example, the probe card assembly 112 in FIG. 1 includes a wiring substrate 202 and a probe substrate 206, which typically are made of different materials and thus have different coefficients of thermal expansion (CTE). Temperature changes or gradients can thus cause the different substrates to expand or contract different amounts. Because the wiring substrate 202 and the probe substrate 206 are coupled together in the probe card assembly 112 in FIG. 2, this can cause the wiring substrate 202 and the probe substrate 206 to warp as shown in FIG. 3. Warping can also be opposite of that shown in FIG. 3. As shown in FIGS. 2 and 3, such warping can change an orientation of the tips of the probes 412. For example, an initial orientation 208 of the tips of the probes 412 can change to a warped orientation 208′. Thermal expansion or contraction of the substrates (e.g., the wiring substrate 202 and the probe substrate 206) of the probe card assembly 112 can cause other problems. For example, electrical connections between the substrates can become misaligned. In the probe card assembly 112 of FIG. 2, for example, electrical connections (not shown) between the wiring substrate 202 and the probe substrate 206 can become misaligned. As another example, the probes 412 can become misaligned with the terminals 116 of the DUTs 118 (see FIG. 1). Some embodiments address one or more of the foregoing problems and/or other problems as described herein.